1. Field of the Invention
This invention relates to lubricant and fuel compositions. More particularly, it relates to di-n-hexyl 1,3-cyclohexanedicarboxylate and its use as a lubricant.
2. Description of the Prior Art
A wide variety of naturally occurring and synthetic oils have been used as lubricants to reduce friction between moving surfaces which are in contact with each other. Although mineral oils have most commonly been used for this purpose, synthetic materials such as olefin polymers, polyoxypropylene and certain carboxylic acid esters and naturally occurring oils such as cottonseed oil, corn oil, castor oil, lard oil and sperm oil have also been used. Typically, such lubricants are employed to lubricate internal combustion engines, gear trains, turbines, compressors and the like.
A satisfactory lubricating oil must possess a unique combination of properties. In particular, the oil must be noncorrosive and have good low temperature fluidity properties in combination with low volatility at elevated temperatures. In addition, good viscosity properties over a wide range of temperatures are highly desirable since proper lubrication in most applications requires that the lubricant be adaptable to changes in temperature without extreme variations in viscosity. Further, lubricants which are utilized at high temperatures, as in gas turbines and four-cycle internal combustion engines, must be resistant to oxidative and thermal degradation.
Two-cycle engines are lubricated by mixing the lubricant with the fuel for the engine. The mixture of fuel and lubricant passes through the crankcase of a two-cycle engine, where it lubricates the moving parts of the engine, and then flows through intake ports into the combustion chamber of the engine where the mixture of fuel and lubricant is burned. Finally, the combustion products are vented from the combustion chamber through exhaust ports. As a consequence, a satisfactory lubricant for two-cycle engines must not only provide adequate lubrication for moving engine parts but also must be able to pass into the combustion chamber without leaving objectionable deposits in the intake ports, must burn cleanly to avoid fouling the combustion chamber and spark plug with undesirable deposits, and must not result in fouling of the exhaust ports.
U.S. Pat. No. 3,701,730 to Daniels et al. discloses that esters of alcohols having 1 to 20 carbon atoms and aliphatic carboxylic acids having 3 to 20 carbon atoms can be used as lubricant base stocks. However, this patent contains no mention of di-n-hexyl 1,3-cyclohexanedicarboxylate and fails to suggest that such a material would be a particularly desirable lubricating oil.
U.S. Pat. No. 2,936,320 to Benoit discloses the use of dialkyl diesters of mixtures of isophthalic acid and terephthalic acid as synthetic lubricating oils. The esters of this patent are derived from alcohols of from 5 to 13 carbon atoms.
U.S. Pat. No. 3,409,553 to Scoggins et al. discloses a two-cycle engine lubricant which comprises a mixture of mineral oil with at least one ester selected from the group consisting of the bis(2-ethylhexyl) esters of 1,2- and 1,3-cyclohexanedicarboxylic acid. Similarly, U.S. Pat. No. 3,251,771 to Benoit discloses the use of dialkyl diesters of 1,4-cyclohexanedicarboxylic acid as a synthetic lubricant base oil. In addition, Matsuda et al. disclose the use of a hydrogenated 3:1 mixture of n-octyl and 2-ethylhexyl isophthalate as a component of a lubricating oil for jet engines at pages 2168-2171 of Kogyo Kagaku Zasshi, Vol. 64 (1961).
Although a plethora of lubricating oils are known to the art, there is no mention in the art of di-n-hexyl 1,3-cyclohexanedicarboxylate and no suggestion that this material would possess an unusually desirable combination of properties which serve to make it exceptionally satisfactory for use as a lubricant and for use as a blending component for lubricant formulations.